This invention relates to a catalytic combustor for a gas turbine.
The purpose of the catalytic combustor of the present invention, as opposed to a simple flame combustor, is to reduce the formation of nitrogen oxides, or NOx. This object is explained in U.S. Pat. No. 5,202,303, the disclosure of which is incorporated herein by reference.
The catalytic combustor in the above-cited patent is a honeycomb comprised of metal strips which are coated with catalyst on just one side. The strips are stacked so that coated sides face each other and uncoated sides face each other. This stack of strips defines a structure in which catalyzed channels alternate with uncatalyzed channels. Only the portion of the fuel-air mixture which flows through the catalyzed channels is combusted within the honeycomb. Since the fuel-air mixture flowing through the uncatalyzed channels is not combusted, the honeycomb is cooled by that portion of the mixture, and the catalyst is not deactivated. Combustion is completed in a flame downstream of the honeycomb. With this configuration, the “window” of time and temperature that makes NOx is avoided.
The present invention provides a structure for a catalytic combustor, which structure reduces the pressure drop through the combustor, and also reduces the stress on the strips where the temperature is highest.